Impulse oscillator



Patented Aug. 6, 1946 IMPULSE OSCILLATOR Emile Labin, New York, N. Y., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application March 13, 1941, Serial No. 383,116

7 Claims. 1

This invention relates to impulse generating and transmitting systems and more particularly to systems in which properly timed impulses are obtained from damped oscillations.

It is often desirable, particularly in distance measuring systems, to transmit energy impulses having a relatively short period of duration compared to the period of oscillation or repetition of the impulse. For such generators a spark gap oscillator would appear to be well suited. It is found, however, that in ordinary spark gap oscillators the duration of the impulse at a particular frequency is not sufficiently controllable and is generally not sufilciently long to make such arrangements practicable.

It is a principal object of my invention to provide a system utilizing spark gap discharge circuits in which the length of impulse at a particular frequency may be readily controlled.

This object may be accomplished according to a feature of my invention by producing a spark gap discharge across a point coupled to one end of a transmission line, the other end of which is terminated in the characteristic impedance of the line. This arrangement will then produce an impulse traveling from the spark gap down the length of the line to the terminating impedance. Along the transmission line at one or more points is coupled a resonant circuit, preferably a hollow resonant cavity for extracting energy at the resonant frequency of the cavity from the discharge current or voltage as it traverses the line. Due to the high Q value of the resonant cavity the duration of the pulse can be made long enough for practical purposes.

While I have broadly set forth the principal object and feature of my invention, a better understanding of my invention and the objects and features thereof may be had from the particular description thereof made in conjunction with the accompanying drawing, in which Fig. 1 illustrates partially in cross-section a circuit in accordance with my invention;

Fig. 2 illustrates a modified embodiment of my invention; and

Fig. 3 represents a different form of impulse generator according to my invention.

In Fig. l, at I0, is shown a source of potential connected across a condenser II. Source II] is preferably an alternating or impulse potential source having a period equal to the desired spacing between the impulses to be produced and a potential sufficiently high to cause a spark discharge over the spark gap terminals I2. Across condenser II is provided a circuit comprising spark gap I2 and a transmission line I3, preferably a coaxial line having an outer conductor I l and an inner conductor I5. At the remote end of transmission line I3 is provided a resistance element It which is made to be equal to the surge impedance or characteristic impedance of the line. As shown in Fig. 1, this resistance is illustrated as a plate coated with a high resistance material. This resistance, however, may take any desired form and may be artificially cooled by a water jacket or the like in order to dissipate heat generated by the energy traversing the resistance. The resistance can also be part of a more complicated dipole taking into account the change in the characteristic impedance of the transmission line due to the coupling with the resonant cavity.

The outer conductor I 4 of the transmission line is provided with a plurality of apertures I'I arranged in spaced longitudinal relationship along the transmission line. Over each opening I1 is provided a resonant cavity shown in Fig. 1 as being substantially spherical in shape. These cavities l 8 serve to extract energy at the resonant frequency thereof from the discharge energy as it traverses transmission line I3. To each of the resonant cavities I8 is coupled an antenna unit I9 forming a dipole radiator.

In operation a voltage is built up by energy supplied from source Ill across condenser II until this voltage is sufficiently high to cause a spark discharge across gap I2. These discharges will be produced periodically depending upon th nature of source Ill. The discharge across gap I2 will produce an impulse which will traverse line 113 to its remote end where it will be absorbed in terminating resistance I6. The discharge impulse traversing line I3 will have a steep wave front and will be highly damped as in most spark discharge systems. Accordingly, because of the form of the discharge it is clear that energy components of various high frequencies will be present in the wave. As the wave caused by the disrupted discharge travels past apertures I7 a portion of the energy will be extracted by resonant cavities I8 and will be radiated from antenna elements I9. By properly choosing the spacing between the apertures and the antenna units the proper phase relationship for obtaining a desired directive effect may be produced directly in the system. For example, if antennae I9 are successively spaced a wavelength apart and it is assumed that the discharge traverses transmission line I3 at the speed of light, then each successive antenna unit will be energized in phase and a so-called broadside array will be produced.

In traversing line l3 the impulse waves may be slightly attenuated as to the frequencies absorbed in resonant circuits I8. However, if this absorption is sufficiently great so as to tend to produce large difierences in theenergization of antennae 19, the losses in resonant chambers [8 may be adjusted to care for this decrease. This may be accomplished by choosing materials or providing a coating on the inner surface of chambers ill, or, preferably, by controlling the coupling between the chambers and the loading so as to have a higher Q in the chamber first traversed by the energy than in the succeeding chamber.

In Fig. 2 a slightly modified arrangement is illustrated. The source [0, condenser I l, and spark gap 12 may be substantially the same as those shown in Fig. 1. Likewise, a similar coaxial transmission line i3 having an inner conductor l5 and outer conductor M is provided. As shown in this figure, the terminating impedance I6 is illustrated as a generalized resistance, although it should be clearly understood that any form of resistance unit may be used. Along the length of outer conductor M are provided a plurality of coupling openings 20. I'he first openings are shown as rectangular in form while those at the center are shown as circular openings. It should be understood that any types of openings may be used, it merely being necessary to provide some apertures for coupling an external circuit to the transmission line. Instead of a plurality of separate chambers, a single resonant cavity 2| is provided. This cavity is coupled with the line at a plurality of places corresponding to openings 20. To cavity 21 is coupled a line 22 so that energy may be furnished to a load circuit. If desired, a plurality of lines 22 may be coupled at spaced points along the surface of cavity 2| to provide differences of phase in the energized circuits.

, In Fig. 3 is shown a preferred type of impulse generator to be used in place of the simple spark gap of Figs. 1 and 2.

I In this figure an end of the cable cut at line AA is shown, comprising inner and outer conductors l3, M, respectively. A source of energy 30 is provided connected at one side to outer conductor M, which conductor is made to extend past 1 the inner conductor [3 and is preferably reduced in diameter beyond the inner conductor. The other terminal of source 30 is connected to a rod 32 provided in spaced relation with central conductor H3. The potential of source 30 is sumciently high to maintain an arc discharge 34 between l3 and 32. This is preferably accomplished by arranging the arc equipment in an atmosphere of inert gas.

A source of energy 3| which is preferably periodic in nature is connected to a pair of deflecting coils 33. When coils 33 are energized are 34 is forced to one side and into contact with the reduced portion of outer conductor 34. Each time the arc contacts 33 and again breaks away from contact a short damped impulse is produced which traverses the transmission line in a manner similar to that described in connection with Figs. 1 and 2. The period of the impulse generation may be controlled by the frequency of pulsation or interruption of energy from source 3!.

While I have described above for the purpose of illustration some structural embodiments of my invention, it should be distinctly understood that these embodiments do not serve and are not intended as limitations of the scope of my invention. Many changes and alterations in the structural details of the system may be made within the spirit of my invention. For example, resonant cavities such as shown at 18, in Fig. 1, may be made in the form of figures of revolution instead of the spherical arrangements shown. Also, many other changes in the type of transmission line used and in the various circuits applied thereto may be provided within the terms of my invention. For example, instead of using a spark gap to produc the impulses traveling from the fed end down to the terminating impedance of the line, it is possible to use any kind of pulse generator, such as an electronic tube generator.

What is claimed is:

1. An electrical impulse generator comprising a two-conductor line, means for terminating one end of said line in its characteristic impedance, means for producing a damped electrical discharge periodically at the unterminated end of said line, whereby electrical impulses will periodically traverse said line to said characteristic impedance means, and a substantially closed resonant chamber coupled to said line to extract a portion of the energy at the resonant frequency of said chamber from said impulses traversing said line.

2. An impulse generating system according to claim 1, wherein said two-conductor line comprises a coaxial line provided with an opening, and said resonant chamber is coupled to said line by fitting over said opening.

3. An impulse generator according to claim 1, wherein said two-conductor line comprises a length of coaxial line provided with a plurality of openings spaced apart along said line, and said substantially closed resonant chamber comprises a single cavity coupled with said line through said spaced openings.

4. A radiating arrangement comprising a twoconductor line, means for terminating one end of said line in its characteristic impedance, means for producing a damped electrical discharge periodically at the unterminated end of said line, whereby electrical impulses will periodically traverse said line to said characteristic impedance means, a substantially closed resonant chamber coupled to said line to extract a portion of the energy at the resonant frequency of said chamber from said impulses traversing said line, and a radiating unit coupled with said resonant chamher.

5. A radiating arrangement compising a twoconductor coaxial transmission line terminated at one end in its characteristic impedance, means for providing a damped electrical discharge periodically at the unterminated end of said transmission line, a plurality of openings in the outer conductor of said transmission line, said openings being spaced longitudinally of said line a predetermined fraction of a wavelength, a plurality of substantially closed resonant cavities fitted over respective ones of said openings to extract energy therefrom during passage of an impulse along said line, and individual radiators coupled to said resonant chambers.

6. An electric impulse generator according to claim 1, wherein said means for producing a damped electrical discharge comprises an are discharge gap provided in one of the conductors of said line, a source of electrical energy connected to said transmission line conductors to maintain an arc discharg across said gap, and periodically operating means for distorting said are periodically into contact with the other conductor of said line whereby damped impulse waves are produced in said line.

'7. An electric impulse generator for use in a two-conductor transmission line comprising an arc discharge gap provided in one of the conductors of said line, a source of electrical energy connected to said transmission line conductors to maintain an arc discharge across said gap, and periodically operating means for distorting said are discharge periodically into contact with the other conductor of said line whereby damped impulse waves are produced in said line.

EMILE LABIN. 

